Summary of Significant Accounting Policies (Narrative) (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2020 USD ($) customer	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) segment customer	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Concentration Risk [Line Items]
Number of reportable segments | segment									3
Allowance for doubtful accounts	$ 5,500,000				$ 4,900,000				$ 5,500,000	$ 4,900,000
Sale of accounts receivable									74,100,000	112,700,000
Expense related to discount on sale of accounts receivable									400,000	1,100,000
Goodwill impairment									0	0	$ 0
Indefinite-lived intangible assets impairment									0	0	0
GILTI, income tax expense									1,800,000	1,900,000
FDII decrease in income tax expense									0.0	800,000
Net sales	360,400,000	$ 340,200,000	$ 228,300,000	$ 366,300,000	$ 379,500,000	$ 403,400,000	$ 415,300,000	$ 420,100,000	1,295,200,000	$ 1,618,300,000	$ 1,658,100,000
Accounts receivable, allowance for credit losses	$ 5,500,000								$ 5,500,000
Six Customers In Automotive Industry | Customer Concentration Risk
Concentration Risk [Line Items]
Uncollateralized accounts receivable, number of customers | customer	6								6
Accounts Receivable | Six Customers In Automotive Industry | Customer Concentration Risk
Concentration Risk [Line Items]
Uncollateralized accounts receivable	$ 40,600,000								$ 40,600,000
Percentage of concentration									16.00%
Revenue from Contract with Customer | Six Customers In Automotive Industry | Customer Concentration Risk
Concentration Risk [Line Items]
Percentage of concentration									18.00%
Net sales									$ 228,200,000